Conventionally, colloidal solutions of tin and palladium and aqueous solutions of palladium chloride and other palladium compounds are used as catalysts in electroless plating. The problem with these catalysts is that because they use inorganic palladium compounds, when using organic solvents which have a better wettability than water and excellent applicability and workability and which can also dissolve other organic compounds such as resins, the solubility is poor and the palladium precipitates without providing a uniform solution. Palladium acetate, which is formed from a lower fatty acid, is soluble in methanol depending on the concentration, but the palladium rapidly precipitates.